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Qiu Y, Kang YM, Korfmann C, Pouyet F, Eckford A, Palazzo AF. The GC-content at the 5' ends of human protein-coding genes is undergoing mutational decay. Genome Biol 2024; 25:219. [PMID: 39138526 PMCID: PMC11323403 DOI: 10.1186/s13059-024-03364-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2024] [Accepted: 07/31/2024] [Indexed: 08/15/2024] Open
Abstract
BACKGROUND In vertebrates, most protein-coding genes have a peak of GC-content near their 5' transcriptional start site (TSS). This feature promotes both the efficient nuclear export and translation of mRNAs. Despite the importance of GC-content for RNA metabolism, its general features, origin, and maintenance remain mysterious. We investigate the evolutionary forces shaping GC-content at the transcriptional start site (TSS) of genes through both comparative genomic analysis of nucleotide substitution rates between different species and by examining human de novo mutations. RESULTS Our data suggests that GC-peaks at TSSs were present in the last common ancestor of amniotes, and likely that of vertebrates. We observe that in apes and rodents, where recombination is directed away from TSSs by PRDM9, GC-content at the 5' end of protein-coding gene is currently undergoing mutational decay. In canids, which lack PRDM9 and perform recombination at TSSs, GC-content at the 5' end of protein-coding is increasing. We show that these patterns extend into the 5' end of the open reading frame, thus impacting synonymous codon position choices. CONCLUSIONS Our results indicate that the dynamics of this GC-peak in amniotes is largely shaped by historic patterns of recombination. Since decay of GC-content towards the mutation rate equilibrium is the default state for non-functional DNA, the observed decrease in GC-content at TSSs in apes and rodents indicates that the GC-peak is not being maintained by selection on most protein-coding genes in those species.
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Affiliation(s)
- Yi Qiu
- Department of Biochemistry, University of Toronto, Toronto, Ontario, M5G1M1, Canada
| | - Yoon Mo Kang
- Department of Biochemistry, University of Toronto, Toronto, Ontario, M5G1M1, Canada
| | - Christopher Korfmann
- Department of Electrical Engineering and Computer Science, York University, Toronto, Ontario, M3J1P3, Canada
| | - Fanny Pouyet
- Laboratoire Interdisciplinaire des Sciences du Numérique, Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Andrew Eckford
- Department of Electrical Engineering and Computer Science, York University, Toronto, Ontario, M3J1P3, Canada
| | - Alexander F Palazzo
- Department of Biochemistry, University of Toronto, Toronto, Ontario, M5G1M1, Canada.
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2
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Luna R, Gómez-González B, Aguilera A. RNA biogenesis and RNA metabolism factors as R-loop suppressors: a hidden role in genome integrity. Genes Dev 2024; 38:504-527. [PMID: 38986581 PMCID: PMC11293400 DOI: 10.1101/gad.351853.124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/12/2024]
Abstract
Genome integrity relies on the accuracy of DNA metabolism, but as appreciated for more than four decades, transcription enhances mutation and recombination frequencies. More recent research provided evidence for a previously unforeseen link between RNA and DNA metabolism, which is often related to the accumulation of DNA-RNA hybrids and R-loops. In addition to physiological roles, R-loops interfere with DNA replication and repair, providing a molecular scenario for the origin of genome instability. Here, we review current knowledge on the multiple RNA factors that prevent or resolve R-loops and consequent transcription-replication conflicts and thus act as modulators of genome dynamics.
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Affiliation(s)
- Rosa Luna
- Andalusian Center of Molecular Biology and Regenerative Medicine (CABIMER), Universidad de Sevilla-Spanish National Research Council (CSIC), 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Belén Gómez-González
- Andalusian Center of Molecular Biology and Regenerative Medicine (CABIMER), Universidad de Sevilla-Spanish National Research Council (CSIC), 41092 Seville, Spain
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
| | - Andrés Aguilera
- Andalusian Center of Molecular Biology and Regenerative Medicine (CABIMER), Universidad de Sevilla-Spanish National Research Council (CSIC), 41092 Seville, Spain;
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, 41012 Seville, Spain
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3
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Xu Y, Jiao Y, Liu C, Miao R, Liu C, Wang Y, Ma C, Liu J. R-loop and diseases: the cell cycle matters. Mol Cancer 2024; 23:84. [PMID: 38678239 PMCID: PMC11055327 DOI: 10.1186/s12943-024-02000-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2024] [Accepted: 04/13/2024] [Indexed: 04/29/2024] Open
Abstract
The cell cycle is a crucial biological process that is involved in cell growth, development, and reproduction. It can be divided into G1, S, G2, and M phases, and each period is closely regulated to ensure the production of two similar daughter cells with the same genetic material. However, many obstacles influence the cell cycle, including the R-loop that is formed throughout this process. R-loop is a triple-stranded structure, composed of an RNA: DNA hybrid and a single DNA strand, which is ubiquitous in organisms from bacteria to mammals. The existence of the R-loop has important significance for the regulation of various physiological processes. However, aberrant accumulation of R-loop due to its limited resolving ability will be detrimental for cells. For example, DNA damage and genomic instability, caused by the R-loop, can activate checkpoints in the cell cycle, which in turn induce cell cycle arrest and cell death. At present, a growing number of factors have been proven to prevent or eliminate the accumulation of R-loop thereby avoiding DNA damage and mutations. Therefore, we need to gain detailed insight into the R-loop resolution factors at different stages of the cell cycle. In this review, we review the current knowledge of factors that play a role in resolving the R-loop at different stages of the cell cycle, as well as how mutations of these factors lead to the onset and progression of diseases.
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Affiliation(s)
- Yuqin Xu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Yue Jiao
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chengbin Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Rui Miao
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chunyan Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Yilong Wang
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Chunming Ma
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China
| | - Jiao Liu
- School of Basic Medicine Sciences, Shandong Second Medical University, Weifang, 261053, China.
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4
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Abugable AA, Antar S, El-Khamisy SF. Chromosomal single-strand break repair and neurological disease: Implications on transcription and emerging genomic tools. DNA Repair (Amst) 2024; 135:103629. [PMID: 38266593 DOI: 10.1016/j.dnarep.2024.103629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Revised: 12/21/2023] [Accepted: 01/04/2024] [Indexed: 01/26/2024]
Abstract
Cells are constantly exposed to various sources of DNA damage that pose a threat to their genomic integrity. One of the most common types of DNA breaks are single-strand breaks (SSBs). Mutations in the repair proteins that are important for repairing SSBs have been reported in several neurological disorders. While several tools have been utilised to investigate SSBs in cells, it was only through recent advances in genomics that we are now beginning to understand the architecture of the non-random distribution of SSBs and their impact on key cellular processes such as transcription and epigenetic remodelling. Here, we discuss our current understanding of the genome-wide distribution of SSBs, their link to neurological disorders and summarise recent technologies to investigate SSBs at the genomic level.
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Affiliation(s)
- Arwa A Abugable
- School of Biosciences, Firth Court, University of Sheffield, Sheffield, UK; The healthy Lifespan and Neuroscience Institutes, University of Sheffield, Sheffield, UK
| | - Sarah Antar
- School of Biosciences, Firth Court, University of Sheffield, Sheffield, UK; The healthy Lifespan and Neuroscience Institutes, University of Sheffield, Sheffield, UK; Medical Biochemistry and Molecular Biology Department, Faculty of Medicine, Mansoura University, Egypt
| | - Sherif F El-Khamisy
- School of Biosciences, Firth Court, University of Sheffield, Sheffield, UK; The healthy Lifespan and Neuroscience Institutes, University of Sheffield, Sheffield, UK; Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford, Bradford, UK.
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5
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Livnat A, Melamed D. Evolutionary honing in and mutational replacement: how long-term directed mutational responses to specific environmental pressures are possible. Theory Biosci 2023; 142:87-105. [PMID: 36899155 PMCID: PMC10209271 DOI: 10.1007/s12064-023-00387-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 01/13/2023] [Indexed: 03/12/2023]
Abstract
Recent results have shown that the human malaria-resistant hemoglobin S mutation originates de novo more frequently in the gene and in the population where it is of adaptive significance, namely, in the hemoglobin subunit beta gene compared to the nonresistant but otherwise identical 20A[Formula: see text]T mutation in the hemoglobin subunit delta gene, and in sub-Saharan Africans, who have been subject to intense malarial pressure for many generations, compared to northern Europeans, who have not. This finding raises a fundamental challenge to the traditional notion of accidental mutation. Here, we address this finding with the replacement hypothesis, according to which preexisting genetic interactions can lead directly and mechanistically to mutations that simplify and replace them. Thus, an evolutionary process under selection can gradually hone in on interactions of importance for the currently evolving adaptations, from which large-effect mutations follow that are relevant to these adaptations. We exemplify this hypothesis using multiple types of mutation, including gene fusion mutations, gene duplication mutations, A[Formula: see text]G mutations in RNA-edited sites and transcription-associated mutations, and place it in the broader context of a system-level view of mutation origination called interaction-based evolution. Potential consequences include that similarity of mutation pressures may contribute to parallel evolution in genetically related species, that the evolution of genome organization may be driven by mutational mechanisms, that transposable element movements may also be explained by replacement, and that long-term directed mutational responses to specific environmental pressures are possible. Such mutational phenomena need to be further tested by future studies in natural and artificial settings.
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Affiliation(s)
- Adi Livnat
- Department of Evolutionary and Environmental Biology, University of Haifa, 3498838, Haifa, Israel.
- Institute of Evolution, University of Haifa, 3498838, Haifa, Israel.
| | - Daniel Melamed
- Department of Evolutionary and Environmental Biology, University of Haifa, 3498838, Haifa, Israel
- Institute of Evolution, University of Haifa, 3498838, Haifa, Israel
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6
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Lamas-Maceiras M, Vizoso-Vázquez Á, Barreiro-Alonso A, Cámara-Quílez M, Cerdán ME. Thanksgiving to Yeast, the HMGB Proteins History from Yeast to Cancer. Microorganisms 2023; 11:microorganisms11040993. [PMID: 37110415 PMCID: PMC10142021 DOI: 10.3390/microorganisms11040993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/03/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
Yeasts have been a part of human life since ancient times in the fermentation of many natural products used for food. In addition, in the 20th century, they became powerful tools to elucidate the functions of eukaryotic cells as soon as the techniques of molecular biology developed. Our molecular understandings of metabolism, cellular transport, DNA repair, gene expression and regulation, and the cell division cycle have all been obtained through biochemistry and genetic analysis using different yeasts. In this review, we summarize the role that yeasts have had in biological discoveries, the use of yeasts as biological tools, as well as past and on-going research projects on HMGB proteins along the way from yeast to cancer.
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Affiliation(s)
- Mónica Lamas-Maceiras
- Centro Interdisciplinar de Química y Biología (CICA), As Carballeiras, s/n, Campus de Elviña, Universidade da Coruña, 15071 A Coruña, Spain
- Instituto de Investigación Biomédica de A Coruña (INIBIC), As Xubias de Arriba 84, 15006 A Coruña, Spain
- Facultad de Ciencias, A Fraga, s/n, Campus de A Zapateira, Universidade da Coruña, 15071 A Coruña, Spain
| | - Ángel Vizoso-Vázquez
- Centro Interdisciplinar de Química y Biología (CICA), As Carballeiras, s/n, Campus de Elviña, Universidade da Coruña, 15071 A Coruña, Spain
- Instituto de Investigación Biomédica de A Coruña (INIBIC), As Xubias de Arriba 84, 15006 A Coruña, Spain
- Facultad de Ciencias, A Fraga, s/n, Campus de A Zapateira, Universidade da Coruña, 15071 A Coruña, Spain
| | - Aida Barreiro-Alonso
- Centro Interdisciplinar de Química y Biología (CICA), As Carballeiras, s/n, Campus de Elviña, Universidade da Coruña, 15071 A Coruña, Spain
- Instituto de Investigación Biomédica de A Coruña (INIBIC), As Xubias de Arriba 84, 15006 A Coruña, Spain
- Facultad de Ciencias, A Fraga, s/n, Campus de A Zapateira, Universidade da Coruña, 15071 A Coruña, Spain
| | - María Cámara-Quílez
- Centro Interdisciplinar de Química y Biología (CICA), As Carballeiras, s/n, Campus de Elviña, Universidade da Coruña, 15071 A Coruña, Spain
- Instituto de Investigación Biomédica de A Coruña (INIBIC), As Xubias de Arriba 84, 15006 A Coruña, Spain
- Facultad de Ciencias, A Fraga, s/n, Campus de A Zapateira, Universidade da Coruña, 15071 A Coruña, Spain
| | - María Esperanza Cerdán
- Centro Interdisciplinar de Química y Biología (CICA), As Carballeiras, s/n, Campus de Elviña, Universidade da Coruña, 15071 A Coruña, Spain
- Instituto de Investigación Biomédica de A Coruña (INIBIC), As Xubias de Arriba 84, 15006 A Coruña, Spain
- Facultad de Ciencias, A Fraga, s/n, Campus de A Zapateira, Universidade da Coruña, 15071 A Coruña, Spain
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7
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Splicing Modulation Results in Aberrant Isoforms and Protein Products of p53 Pathway Genes and the Sensitization of B Cells to Non-Genotoxic MDM2 Inhibition. Int J Mol Sci 2023; 24:ijms24032410. [PMID: 36768733 PMCID: PMC9916657 DOI: 10.3390/ijms24032410] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/18/2023] [Accepted: 01/24/2023] [Indexed: 01/27/2023] Open
Abstract
Several molecular subtypes of cancer are highly dependent on splicing for cell survival. There is a general interest in the therapeutic targeting of splicing by small molecules. E7107, a first-in-class spliceosome inhibitor, showed strong growth inhibitory activities against a large variety of human cancer xenografts. Chronic lymphocytic leukaemia (CLL) is a clinically heterogeneous hematologic malignancy, with approximately 90% of cases being TP53 wild-type at diagnosis. An increasing number of studies are evaluating alternative targeted agents in CLL, including MDM2-p53 binding antagonists. In this study, we report the effect of splicing modulation on key proteins in the p53 signalling pathway, an important cell death pathway in B cells. Splicing modulation by E7107 treatment reduced full-length MDM2 production due to exon skipping, generating a consequent reciprocal p53 increase in TP53WT cells. It was especially noteworthy that a novel p21WAF1 isoform with compromised cyclin-dependent kinase inhibitory activity was produced due to intron retention. E7107 synergized with the MDM2 inhibitor RG7388, via dual MDM2 inhibition; by E7107 at the transcript level and by RG7388 at the protein level, producing greater p53 stabilisation and apoptosis. This study provides evidence for a synergistic MDM2 and spliceosome inhibitor combination as a novel approach to treat CLL and potentially other haematological malignancies.
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8
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Lu H, Yang M, Zhou Q. Reprogramming transcription after DNA damage: recognition, response, repair, and restart. Trends Cell Biol 2022:S0962-8924(22)00261-6. [PMID: 36513571 DOI: 10.1016/j.tcb.2022.11.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 11/20/2022] [Accepted: 11/24/2022] [Indexed: 12/14/2022]
Abstract
Genome integrity is constantly challenged by endogenous and exogenous insults that cause DNA damage. To cope with these threats, cells have a surveillance mechanism, known as the DNA damage response (DDR), to repair any lesions. Although transcription has long been implicated in DNA repair, how transcriptional reprogramming is coordinated with the DDR is just beginning to be understood. In this review, we highlight recent advances in elucidating the molecular mechanisms underlying major transcriptional events, including RNA polymerase (Pol) II stalling and transcriptional silencing and recovery, which occur in response to DNA damage. Furthermore, we discuss how such transcriptional adaptation contributes to sensing and eliminating damaged DNA and how it can jeopardize genome integrity when it goes awry.
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Affiliation(s)
- Huasong Lu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China.
| | - Min Yang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, Zhejiang 310058, China
| | - Qiang Zhou
- School of Biological Sciences, Faculty of Science, The University of Hong Kong, Hong Kong.
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9
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Zhang X, Hooykaas MJG, van Heusden GP, Hooykaas PJJ. The translocated virulence protein VirD5 causes DNA damage and mutation during Agrobacterium-mediated transformation of yeast. SCIENCE ADVANCES 2022; 8:eadd3912. [PMID: 36383666 PMCID: PMC9668295 DOI: 10.1126/sciadv.add3912] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 09/27/2022] [Indexed: 06/16/2023]
Abstract
The soil bacterium Agrobacterium tumefaciens is a preferred gene vector not only for plants but also for fungi. Agrobacterium delivers a small set of virulence proteins into host cells concomitantly with transferred DNA (T-DNA) to support the transformation process. Here, we find that expression of one of these proteins, called VirD5, in yeast host cells causes replication stress and DNA damage. This can result in both genomic rearrangements and local mutations, especially small deletions. Delivery of VirD5 during cocultivation with Agrobacterium led to mutations in the yeast genome that were unlinked to the integration of T-DNA. This load of mutations can be prevented by using a virD5 mutant for genome engineering, but this leads to a lower transformation frequency.
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10
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Abstract
The enormous diversity of antibodies is a key element to combat infections. Antibodies containing pathogen receptors were a surprising discovery that contrasted antibody diversification through classic recombination events. However, such insert-containing antibodies were thus far exclusively detected in African individuals exposed to malaria parasites and were identified as screening byproducts or through hypothesis-driven search. The prevalence and complexity of insertion events remained elusive. In this study, we devise an unbiased, systematic approach to identify inserts in the human antibody repertoire. We show that inserts from distant genomic regions occur in the majority of donors and are independent of Plasmodium falciparum preexposure. Our findings suggest that four distinct classes of insertion events contribute diversity to the human antibody repertoire. Recombination of antibody genes in B cells can involve distant genomic loci and contribute a foreign antigen-binding element to form hybrid antibodies with broad reactivity for Plasmodium falciparum. So far, antibodies containing the extracellular domain of the LAIR1 and LILRB1 receptors represent unique examples of cross-chromosomal antibody diversification. Here, we devise a technique to profile non-VDJ elements from distant genes in antibody transcripts. Independent of the preexposure of donors to malaria parasites, non-VDJ inserts were detected in 80% of individuals at frequencies of 1 in 104 to 105 B cells. We detected insertions in heavy, but not in light chain or T cell receptor transcripts. We classify the insertions into four types depending on the insert origin and destination: 1) mitochondrial and 2) nuclear DNA inserts integrated at VDJ junctions; 3) inserts originating from telomere proximal genes; and 4) fragile sites incorporated between J-to-constant junctions. The latter class of inserts was exclusively found in memory and in in vitro activated B cells, while all other classes were already detected in naïve B cells. More than 10% of inserts preserved the reading frame, including transcripts with signs of antigen-driven affinity maturation. Collectively, our study unravels a mechanism of antibody diversification that is layered on the classical V(D)J and switch recombination.
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11
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Mehta S, Zhang J. Liquid-liquid phase separation drives cellular function and dysfunction in cancer. Nat Rev Cancer 2022; 22:239-252. [PMID: 35149762 PMCID: PMC10036213 DOI: 10.1038/s41568-022-00444-7] [Citation(s) in RCA: 119] [Impact Index Per Article: 59.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/12/2022] [Indexed: 12/11/2022]
Abstract
Cancer is a disease of uncontrollably reproducing cells. It is governed by biochemical pathways that have escaped the regulatory bounds of normal homeostatic balance. This balance is maintained through precise spatiotemporal regulation of these pathways. The formation of biomolecular condensates via liquid-liquid phase separation (LLPS) has recently emerged as a widespread mechanism underlying the spatiotemporal coordination of biological activities in cells. Biomolecular condensates are widely observed to directly regulate key cellular processes involved in cancer cell pathology, and the dysregulation of LLPS is increasingly implicated as a previously hidden driver of oncogenic activity. In this Perspective, we discuss how LLPS shapes the biochemical landscape of cancer cells.
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Affiliation(s)
- Sohum Mehta
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
| | - Jin Zhang
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA.
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA.
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA.
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12
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Tutaj H, Pirog A, Tomala K, Korona R. Genome-scale patterns in the loss of heterozygosity incidence in Saccharomyces cerevisiae. Genetics 2022; 221:6536968. [PMID: 35212738 PMCID: PMC9071580 DOI: 10.1093/genetics/iyac032] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/17/2022] [Indexed: 02/07/2023] Open
Abstract
Former studies have established that loss of heterozygosity can be a key driver of sequence evolution in unicellular eukaryotes and tissues of metazoans. However, little is known about whether the distribution of loss of heterozygosity events is largely random or forms discernible patterns across genomes. To initiate our experiments, we introduced selectable markers to both arms of all chromosomes of the budding yeast. Subsequent extensive assays, repeated over several genetic backgrounds and environments, provided a wealth of information on the genetic and environmental determinants of loss of heterozygosity. Three findings stand out. First, the number of loss of heterozygosity events per unit time was more than 25 times higher for growing than starving cells. Second, loss of heterozygosity was most frequent when regions of homology around a recombination site were identical, about a half-% sequence divergence was sufficient to reduce its incidence. Finally, the density of loss of heterozygosity events was highly dependent on the genome's physical architecture. It was several-fold higher on short chromosomal arms than on long ones. Comparably large differences were seen within a single arm where regions close to a centromere were visibly less affected than regions close, though usually not strictly adjacent, to a telomere. We suggest that the observed uneven distribution of loss of heterozygosity events could have been caused not only by an uneven density of initial DNA damages. Location-depended differences in the mode of DNA repair, or its effect on fitness, were likely to operate as well.
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Affiliation(s)
- Hanna Tutaj
- Institute of Environmental Sciences, Jagiellonian University, 30-387 Cracow, Poland
| | - Adrian Pirog
- Institute of Environmental Sciences, Jagiellonian University, 30-387 Cracow, Poland
| | - Katarzyna Tomala
- Institute of Environmental Sciences, Jagiellonian University, 30-387 Cracow, Poland
| | - Ryszard Korona
- Institute of Environmental Sciences, Jagiellonian University, 30-387 Cracow, Poland,Corresponding author: Institute of Environmental Sciences, Jagiellonian University, Gronostajowa Street 7, 30-387 Krakow, Poland.
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13
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Palazzo AF, Kejiou NS. Non-Darwinian Molecular Biology. Front Genet 2022; 13:831068. [PMID: 35251134 PMCID: PMC8888898 DOI: 10.3389/fgene.2022.831068] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 01/24/2022] [Indexed: 12/14/2022] Open
Abstract
With the discovery of the double helical structure of DNA, a shift occurred in how biologists investigated questions surrounding cellular processes, such as protein synthesis. Instead of viewing biological activity through the lens of chemical reactions, this new field used biological information to gain a new profound view of how biological systems work. Molecular biologists asked new types of questions that would have been inconceivable to the older generation of researchers, such as how cellular machineries convert inherited biological information into functional molecules like proteins. This new focus on biological information also gave molecular biologists a way to link their findings to concepts developed by genetics and the modern synthesis. However, by the late 1960s this all changed. Elevated rates of mutation, unsustainable genetic loads, and high levels of variation in populations, challenged Darwinian evolution, a central tenant of the modern synthesis, where adaptation was the main driver of evolutionary change. Building on these findings, Motoo Kimura advanced the neutral theory of molecular evolution, which advocates that selection in multicellular eukaryotes is weak and that most genomic changes are neutral and due to random drift. This was further elaborated by Jack King and Thomas Jukes, in their paper “Non-Darwinian Evolution”, where they pointed out that the observed changes seen in proteins and the types of polymorphisms observed in populations only become understandable when we take into account biochemistry and Kimura’s new theory. Fifty years later, most molecular biologists remain unaware of these fundamental advances. Their adaptionist viewpoint fails to explain data collected from new powerful technologies which can detect exceedingly rare biochemical events. For example, high throughput sequencing routinely detects RNA transcripts being produced from almost the entire genome yet are present less than one copy per thousand cells and appear to lack any function. Molecular biologists must now reincorporate ideas from classical biochemistry and absorb modern concepts from molecular evolution, to craft a new lens through which they can evaluate the functionality of transcriptional units, and make sense of our messy, intricate, and complicated genome.
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14
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R-loop proximity proteomics identifies a role of DDX41 in transcription-associated genomic instability. Nat Commun 2021; 12:7314. [PMID: 34916496 PMCID: PMC8677849 DOI: 10.1038/s41467-021-27530-y] [Citation(s) in RCA: 69] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 11/24/2021] [Indexed: 12/13/2022] Open
Abstract
Transcription poses a threat to genomic stability through the formation of R-loops that can obstruct progression of replication forks. R-loops are three-stranded nucleic acid structures formed by an RNA-DNA hybrid with a displaced non-template DNA strand. We developed RNA-DNA Proximity Proteomics to map the R-loop proximal proteome of human cells using quantitative mass spectrometry. We implicate different cellular proteins in R-loop regulation and identify a role of the tumor suppressor DDX41 in opposing R-loop and double strand DNA break accumulation in promoters. DDX41 is enriched in promoter regions in vivo, and can unwind RNA-DNA hybrids in vitro. R-loop accumulation upon loss of DDX41 is accompanied with replication stress, an increase in the formation of double strand DNA breaks and transcriptome changes associated with the inflammatory response. Germline loss-of-function mutations in DDX41 lead to predisposition to acute myeloid leukemia in adulthood. We propose that R-loop accumulation and genomic instability-associated inflammatory response may contribute to the development of familial AML with mutated DDX41.
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15
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Medium levels of transcription and replication related chromosomal instability are associated with poor clinical outcome. Sci Rep 2021; 11:23429. [PMID: 34873180 PMCID: PMC8648741 DOI: 10.1038/s41598-021-02787-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 11/08/2021] [Indexed: 11/09/2022] Open
Abstract
Genomic instability (GI) influences treatment efficacy and resistance, and an accurate measure of it is lacking. Current measures of GI are based on counts of specific structural variation (SV) and mutational signatures. Here, we present a holistic approach to measuring GI based on the quantification of the steady-state equilibrium between DNA damage and repair as assessed by the residual breakpoints (BP) remaining after repair, irrespective of SV type. We use the notion of Hscore, a BP "hotspotness" magnitude scale, to measure the propensity of genomic structural or functional DNA elements to break more than expected by chance. We then derived new measures of transcription- and replication-associated GI that we call iTRAC (transcription-associated chromosomal instability index) and iRACIN (replication-associated chromosomal instability index). We show that iTRAC and iRACIN are predictive of metastatic relapse in Leiomyosarcoma (LMS) and that they may be combined to form a new classifier called MAGIC (mixed transcription- and replication-associated genomic instability classifier). MAGIC outperforms the gold standards FNCLCC and CINSARC in stratifying metastatic risk in LMS. Furthermore, iTRAC stratifies chemotherapeutic response in LMS. We finally show that this approach is applicable to other cancers.
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16
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Ortega P, Gómez-González B, Aguilera A. Heterogeneity of DNA damage incidence and repair in different chromatin contexts. DNA Repair (Amst) 2021; 107:103210. [PMID: 34416542 DOI: 10.1016/j.dnarep.2021.103210] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/02/2021] [Accepted: 08/11/2021] [Indexed: 11/18/2022]
Abstract
It has been long known that some regions of the genome are more susceptible to damage and mutagenicity than others. Recent advances have determined a critical role of chromatin both in the incidence of damage and in its repair. Thus, chromatin arises as a guardian of the stability of the genome, which is altered in cancer cells. In this review, we focus into the mechanisms by which chromatin influences the occurrence and repair of the most cytotoxic DNA lesions, double-strand breaks, in particular at actively transcribed chromatin or related to DNA replication.
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Affiliation(s)
- Pedro Ortega
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain; Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
| | - Belén Gómez-González
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain; Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain.
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville, Spain; Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Seville, Spain
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17
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Heterogeneity among enhancer RNAs: origins, consequences and perspectives. Essays Biochem 2021; 65:709-721. [PMID: 34414426 DOI: 10.1042/ebc20200064] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 07/28/2021] [Accepted: 08/06/2021] [Indexed: 12/15/2022]
Abstract
Enhancer RNAs (eRNAs) are non-coding RNAs transcribed from distal cis-regulatory elements (i.e. enhancers), which are stereotyped as short, rarely spliced and unstable. In fact, a non-negligible fraction of eRNAs seems to be longer, spliced and more stable, and their cognate enhancers are epigenomically and functionally distinguishable from typical enhancers. In this review, we first summarized the genomic and molecular origins underlying the observed heterogeneity among eRNAs. Then, we discussed how their heterogeneous properties (e.g. stability) affect the modes of interaction with their regulatory partners, from promiscuous cis-interactions to specific trans-interactions. Finally, we highlighted the existence of a seemingly continuous spectrum of eRNA properties and its implications in the genomic origins of non-coding RNA genes from an evolutionary perspective.
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18
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Rosario R, Anderson R. The molecular mechanisms that underlie fragile X-associated premature ovarian insufficiency: is it RNA or protein based? Mol Hum Reprod 2021; 26:727-737. [PMID: 32777047 PMCID: PMC7566375 DOI: 10.1093/molehr/gaaa057] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/03/2020] [Indexed: 01/30/2023] Open
Abstract
The FMR1 gene contains a polymorphic CGG trinucleotide sequence within its 5′ untranslated region. More than 200 CGG repeats (termed a full mutation) underlie the severe neurodevelopmental condition fragile X syndrome, while repeat lengths that range between 55 and 200 (termed a premutation) result in the conditions fragile X-associated tremor/ataxia syndrome and fragile X-associated premature ovarian insufficiency (FXPOI). Premutations in FMR1 are the most common monogenic cause of premature ovarian insufficiency and are routinely tested for clinically; however, the mechanisms that contribute to the pathology are still largely unclear. As studies in this field move towards unravelling the molecular mechanisms involved in FXPOI aetiology, we review the evidence surrounding the two main theories which describe an RNA toxic gain-of-function mechanism, resulting in the loss of function of RNA-binding proteins, or a protein-based mechanism, where repeat-associated non-AUG translation leads to the formation of an abnormal polyglycine containing protein, called FMRpolyG.
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Affiliation(s)
- Roseanne Rosario
- MRC Centre for Reproductive Health, Queens Medical Research Institute, University of Edinburgh, Edinburgh, UK
| | - Richard Anderson
- MRC Centre for Reproductive Health, Queens Medical Research Institute, University of Edinburgh, Edinburgh, UK
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19
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Uruci S, Lo CSY, Wheeler D, Taneja N. R-Loops and Its Chro-Mates: The Strange Case of Dr. Jekyll and Mr. Hyde. Int J Mol Sci 2021; 22:ijms22168850. [PMID: 34445553 PMCID: PMC8396322 DOI: 10.3390/ijms22168850] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 08/04/2021] [Accepted: 08/12/2021] [Indexed: 12/22/2022] Open
Abstract
Since their discovery, R-loops have been associated with both physiological and pathological functions that are conserved across species. R-loops are a source of replication stress and genome instability, as seen in neurodegenerative disorders and cancer. In response, cells have evolved pathways to prevent R-loop accumulation as well as to resolve them. A growing body of evidence correlates R-loop accumulation with changes in the epigenetic landscape. However, the role of chromatin modification and remodeling in R-loops homeostasis remains unclear. This review covers various mechanisms precluding R-loop accumulation and highlights the role of chromatin modifiers and remodelers in facilitating timely R-loop resolution. We also discuss the enigmatic role of RNA:DNA hybrids in facilitating DNA repair, epigenetic landscape and the potential role of replication fork preservation pathways, active fork stability and stalled fork protection pathways, in avoiding replication-transcription conflicts. Finally, we discuss the potential role of several Chro-Mates (chromatin modifiers and remodelers) in the likely differentiation between persistent/detrimental R-loops and transient/benign R-loops that assist in various physiological processes relevant for therapeutic interventions.
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Affiliation(s)
- Sidrit Uruci
- Department of Molecular Genetics, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands; (S.U.); (C.S.Y.L.)
| | - Calvin Shun Yu Lo
- Department of Molecular Genetics, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands; (S.U.); (C.S.Y.L.)
| | - David Wheeler
- Laboratory of Biochemistry and Molecular Biology, National Cancer Institute, NIH, Bethesda, MD 20892, USA;
| | - Nitika Taneja
- Department of Molecular Genetics, Erasmus MC Cancer Institute, Erasmus University Medical Center, 3000 CA Rotterdam, The Netherlands; (S.U.); (C.S.Y.L.)
- Correspondence:
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20
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Stead ER, Bjedov I. Balancing DNA repair to prevent ageing and cancer. Exp Cell Res 2021; 405:112679. [PMID: 34102225 PMCID: PMC8361780 DOI: 10.1016/j.yexcr.2021.112679] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 04/25/2021] [Accepted: 04/29/2021] [Indexed: 02/06/2023]
Abstract
DNA damage is a constant stressor to the cell. Persistent damage to the DNA over time results in an increased risk of mutation and an accumulation of mutations with age. Loss of efficient DNA damage repair can lead to accelerated ageing phenotypes or an increased cancer risk, and the trade-off between cancer susceptibility and longevity is often driven by the cell's response to DNA damage. High levels of mutations in DNA repair mutants often leads to excessive cell death and stem cell exhaustion which may promote premature ageing. Stem cells themselves have distinct characteristics that enable them to retain low mutation rates. However, when mutations do arise, stem cell clonal expansion can also contribute to age-related tissue dysfunction as well as heightened cancer risk. In this review, we will highlight increasing DNA damage and mutation accumulation as hallmarks common to both ageing and cancer. We will propose that anti-ageing interventions might be cancer preventative and discuss the mechanisms through which they may act.
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Affiliation(s)
- Eleanor Rachel Stead
- UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street London, London WC1E 6DD, UK
| | - Ivana Bjedov
- UCL Cancer Institute, Paul O'Gorman Building, University College London, 72 Huntley Street London, London WC1E 6DD, UK; University College London, Department of Medical Physics and Biomedical Engineering, Malet Place Engineering Building, Gower Street, London WC1E 6BT, UK.
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21
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Ellis DA, Reyes-Martín F, Rodríguez-López M, Cotobal C, Sun XM, Saintain Q, Jeffares DC, Marguerat S, Tallada VA, Bähler J. R-loops and regulatory changes in chronologically ageing fission yeast cells drive non-random patterns of genome rearrangements. PLoS Genet 2021; 17:e1009784. [PMID: 34464389 PMCID: PMC8437301 DOI: 10.1371/journal.pgen.1009784] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 09/13/2021] [Accepted: 08/18/2021] [Indexed: 12/03/2022] Open
Abstract
Aberrant repair of DNA double-strand breaks can recombine distant chromosomal breakpoints. Chromosomal rearrangements compromise genome function and are a hallmark of ageing. Rearrangements are challenging to detect in non-dividing cell populations, because they reflect individually rare, heterogeneous events. The genomic distribution of de novo rearrangements in non-dividing cells, and their dynamics during ageing, remain therefore poorly characterized. Studies of genomic instability during ageing have focussed on mitochondrial DNA, small genetic variants, or proliferating cells. To characterize genome rearrangements during cellular ageing in non-dividing cells, we interrogated a single diagnostic measure, DNA breakpoint junctions, using Schizosaccharomyces pombe as a model system. Aberrant DNA junctions that accumulated with age were associated with microhomology sequences and R-loops. Global hotspots for age-associated breakpoint formation were evident near telomeric genes and linked to remote breakpoints elsewhere in the genome, including the mitochondrial chromosome. Formation of breakpoint junctions at global hotspots was inhibited by the Sir2 histone deacetylase and might be triggered by an age-dependent de-repression of chromatin silencing. An unexpected mechanism of genomic instability may cause more local hotspots: age-associated reduction in an RNA-binding protein triggering R-loops at target loci. This result suggests that biological processes other than transcription or replication can drive genome rearrangements. Notably, we detected similar signatures of genome rearrangements that accumulated in old brain cells of humans. These findings provide insights into the unique patterns and possible mechanisms of genome rearrangements in non-dividing cells, which can be promoted by ageing-related changes in gene-regulatory proteins.
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Affiliation(s)
- David A. Ellis
- Institute of Healthy Ageing, Department of Genetics, Evolution & Environment, University College London, London, United Kingdom
| | - Félix Reyes-Martín
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/Consejo Superior de Investigaciones Científicas, Seville, Spain
| | - María Rodríguez-López
- Institute of Healthy Ageing, Department of Genetics, Evolution & Environment, University College London, London, United Kingdom
| | - Cristina Cotobal
- Institute of Healthy Ageing, Department of Genetics, Evolution & Environment, University College London, London, United Kingdom
| | - Xi-Ming Sun
- MRC London Institute of Medical Sciences, London, United Kingdom
- Institute of Clinical Sciences, Imperial College London, London, United Kingdom
| | - Quentin Saintain
- Institute of Healthy Ageing, Department of Genetics, Evolution & Environment, University College London, London, United Kingdom
| | - Daniel C. Jeffares
- Institute of Healthy Ageing, Department of Genetics, Evolution & Environment, University College London, London, United Kingdom
| | - Samuel Marguerat
- MRC London Institute of Medical Sciences, London, United Kingdom
- Institute of Clinical Sciences, Imperial College London, London, United Kingdom
| | - Víctor A. Tallada
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/Consejo Superior de Investigaciones Científicas, Seville, Spain
| | - Jürg Bähler
- Institute of Healthy Ageing, Department of Genetics, Evolution & Environment, University College London, London, United Kingdom
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22
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Yuan W, Al-Hadid Q, Wang Z, Shen L, Cho H, Wu X, Yang Y. TDRD3 promotes DHX9 chromatin recruitment and R-loop resolution. Nucleic Acids Res 2021; 49:8573-8591. [PMID: 34329467 PMCID: PMC8421139 DOI: 10.1093/nar/gkab642] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2020] [Revised: 06/14/2021] [Accepted: 07/19/2021] [Indexed: 11/12/2022] Open
Abstract
R-loops, which consist of a DNA/RNA hybrid and a displaced single-stranded DNA (ssDNA), are increasingly recognized as critical regulators of chromatin biology. R-loops are particularly enriched at gene promoters, where they play important roles in regulating gene expression. However, the molecular mechanisms that control promoter-associated R-loops remain unclear. The epigenetic ‘reader’ Tudor domain-containing protein 3 (TDRD3), which recognizes methylarginine marks on histones and on the C-terminal domain of RNA polymerase II, was previously shown to recruit DNA topoisomerase 3B (TOP3B) to relax negatively supercoiled DNA and prevent R-loop formation. Here, we further characterize the function of TDRD3 in R-loop metabolism and introduce the DExH-box helicase 9 (DHX9) as a novel interaction partner of the TDRD3/TOP3B complex. TDRD3 directly interacts with DHX9 via its Tudor domain. This interaction is important for recruiting DHX9 to target gene promoters, where it resolves R-loops in a helicase activity-dependent manner to facilitate gene expression. Additionally, TDRD3 also stimulates the helicase activity of DHX9. This stimulation relies on the OB-fold of TDRD3, which likely binds the ssDNA in the R-loop structure. Thus, DHX9 functions together with TOP3B to suppress promoter-associated R-loops. Collectively, these findings reveal new functions of TDRD3 and provide important mechanistic insights into the regulation of R-loop metabolism.
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Affiliation(s)
- Wei Yuan
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope National Cancer Center, Duarte, CA 91010, USA
| | - Qais Al-Hadid
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope National Cancer Center, Duarte, CA 91010, USA
| | - Zhihao Wang
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope National Cancer Center, Duarte, CA 91010, USA
| | - Lei Shen
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope National Cancer Center, Duarte, CA 91010, USA
| | - Hyejin Cho
- Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope National Cancer Center, Duarte, CA 91010, USA
| | - Xiwei Wu
- Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope National Cancer Center, Duarte, CA 91010, USA
| | - Yanzhong Yang
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute, City of Hope National Cancer Center, Duarte, CA 91010, USA
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23
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San Martin-Alonso M, Soler-Oliva ME, García-Rubio M, García-Muse T, Aguilera A. Harmful R-loops are prevented via different cell cycle-specific mechanisms. Nat Commun 2021; 12:4451. [PMID: 34294712 PMCID: PMC8298424 DOI: 10.1038/s41467-021-24737-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 07/01/2021] [Indexed: 12/13/2022] Open
Abstract
Identifying how R-loops are generated is crucial to know how transcription compromises genome integrity. We show by genome-wide analysis of conditional yeast mutants that the THO transcription complex, prevents R-loop formation in G1 and S-phase, whereas the Sen1 DNA-RNA helicase prevents them only in S-phase. Interestingly, damage accumulates asymmetrically downstream of the replication fork in sen1 cells but symmetrically in the hpr1 THO mutant. Our results indicate that: R-loops form co-transcriptionally independently of DNA replication; that THO is a general and cell-cycle independent safeguard against R-loops, and that Sen1, in contrast to previously believed, is an S-phase-specific R-loop resolvase. These conclusions have important implications for the mechanism of R-loop formation and the role of other factors reported to affect on R-loop homeostasis.
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Affiliation(s)
- Marta San Martin-Alonso
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-UPO, Seville, Spain
| | - María E Soler-Oliva
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-UPO, Seville, Spain
| | - María García-Rubio
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-UPO, Seville, Spain
| | - Tatiana García-Muse
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-UPO, Seville, Spain.
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC-UPO, Seville, Spain.
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24
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Bossaert M, Pipier A, Riou JF, Noirot C, Nguyên LT, Serre RF, Bouchez O, Defrancq E, Calsou P, Britton S, Gomez D. Transcription-associated topoisomerase 2α (TOP2A) activity is a major effector of cytotoxicity induced by G-quadruplex ligands. eLife 2021; 10:65184. [PMID: 34180392 PMCID: PMC8279764 DOI: 10.7554/elife.65184] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Accepted: 06/16/2021] [Indexed: 12/11/2022] Open
Abstract
G-quadruplexes (G4) are non-canonical DNA structures found in the genome of most species including human. Small molecules stabilizing these structures, called G4 ligands, have been identified and, for some of them, shown to induce cytotoxic DNA double-strand breaks. Through the use of an unbiased genetic approach, we identify here topoisomerase 2α (TOP2A) as a major effector of cytotoxicity induced by two clastogenic G4 ligands, pyridostatin and CX-5461, the latter molecule currently undergoing phase I/II clinical trials in oncology. We show that both TOP2 activity and transcription account for DNA break production following G4 ligand treatments. In contrast, clastogenic activity of these G4 ligands is countered by topoisomerase 1 (TOP1), which limits co-transcriptional G4 formation, and by factors promoting transcriptional elongation. Altogether our results support that clastogenic G4 ligands act as DNA structure-driven TOP2 poisons at transcribed regions bearing G4 structures.
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Affiliation(s)
- Madeleine Bossaert
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.,Equipe Labellisée Ligue Contre le Cancer 2018, Toulouse, France
| | - Angélique Pipier
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.,Equipe Labellisée Ligue Contre le Cancer 2018, Toulouse, France
| | - Jean-Francois Riou
- Structure et Instabilité des Génomes, Muséum National d'Histoire Naturelle, CNRS, INSERM, Paris, France
| | - Céline Noirot
- INRAE, UR 875, Unité de Mathématique et Informatique Appliquées, Genotoul Bioinfo, Castanet-Tolosan, France
| | - Linh-Trang Nguyên
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France
| | | | - Olivier Bouchez
- INRAE, US 1426, GeT-PlaGe, Genotoul, Castanet-Tolosan, France
| | - Eric Defrancq
- Département de Chimie Moléculaire, UMR CNRS 5250, Université Grenoble Alpes, Grenoble, France
| | - Patrick Calsou
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.,Equipe Labellisée Ligue Contre le Cancer 2018, Toulouse, France
| | - Sébastien Britton
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.,Equipe Labellisée Ligue Contre le Cancer 2018, Toulouse, France
| | - Dennis Gomez
- Institut de Pharmacologie et Biologie Structurale, IPBS, Université de Toulouse, CNRS, UPS, Toulouse, France.,Equipe Labellisée Ligue Contre le Cancer 2018, Toulouse, France
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25
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Perfecting DNA double-strand break repair on transcribed chromatin. Essays Biochem 2021; 64:705-719. [PMID: 32309851 DOI: 10.1042/ebc20190094] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 03/29/2020] [Accepted: 04/01/2020] [Indexed: 02/07/2023]
Abstract
Timely repair of DNA double-strand break (DSB) entails coordination with the local higher order chromatin structure and its transaction activities, including transcription. Recent studies are uncovering how DSBs trigger transient suppression of nearby transcription to permit faithful DNA repair, failing of which leads to elevated chromosomal aberrations and cell hypersensitivity to DNA damage. Here, we summarize the molecular bases for transcriptional control during DSB metabolism, and discuss how the exquisite coordination between the two DNA-templated processes may underlie maintenance of genome stability and cell homeostasis.
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26
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Spector LP, Tiffany M, Ferraro NM, Abell NS, Montgomery SB, Kay MA. Evaluating the Genomic Parameters Governing rAAV-Mediated Homologous Recombination. Mol Ther 2021; 29:1028-1046. [PMID: 33248247 PMCID: PMC7934627 DOI: 10.1016/j.ymthe.2020.11.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 10/16/2020] [Accepted: 11/18/2020] [Indexed: 12/26/2022] Open
Abstract
Recombinant adeno-associated virus (rAAV) vectors have the unique ability to promote targeted integration of transgenes via homologous recombination at specified genomic sites, reaching frequencies of 0.1%-1%. We studied genomic parameters that influence targeting efficiencies on a large scale. To do this, we generated more than 1,000 engineered, doxycycline-inducible target sites in the human HAP1 cell line and infected this polyclonal population with a library of AAV-DJ targeting vectors, with each carrying a unique barcode. The heterogeneity of barcode integration at each target site provided an assessment of targeting efficiency at that locus. We compared targeting efficiency with and without target site transcription for identical chromosomal positions. Targeting efficiency was enhanced by target site transcription, while chromatin accessibility was associated with an increased likelihood of targeting. ChromHMM chromatin states characterizing transcription and enhancers in wild-type K562 cells were also associated with increased AAV-HR efficiency with and without target site transcription, respectively. Furthermore, the amenability of a site to targeting was influenced by the endogenous transcriptional level of intersecting genes. These results define important parameters that may not only assist in designing optimal targeting vectors for genome editing, but also provide new insights into the mechanism of AAV-mediated homologous recombination.
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Affiliation(s)
- Laura P Spector
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Matthew Tiffany
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA
| | - Nicole M Ferraro
- Biomedical Informatics Program, Stanford University School of Medicine, Stanford, CA, USA
| | - Nathan S Abell
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA
| | - Stephen B Montgomery
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Mark A Kay
- Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA.
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27
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Palazzo AF, Kang YM. GC-content biases in protein-coding genes act as an "mRNA identity" feature for nuclear export. Bioessays 2020; 43:e2000197. [PMID: 33165929 DOI: 10.1002/bies.202000197] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 09/30/2020] [Accepted: 10/01/2020] [Indexed: 01/11/2023]
Abstract
It has long been observed that human protein-coding genes have a particular distribution of GC-content: the 5' end of these genes has high GC-content while the 3' end has low GC-content. In 2012, it was proposed that this pattern of GC-content could act as an mRNA identity feature that would lead to it being better recognized by the cellular machinery to promote its nuclear export. In contrast, junk RNA, which largely lacks this feature, would be retained in the nucleus and targeted for decay. Now two recent papers have provided evidence that GC-content does promote the nuclear export of many mRNAs in human cells.
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Affiliation(s)
- Alexander F Palazzo
- Department of Biochemistry, University of Toronto, Toronto, ON, M5G 1M1, Canada
| | - Yoon Mo Kang
- Department of Biochemistry, University of Toronto, Toronto, ON, M5G 1M1, Canada
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28
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Qin L, Li D, Zhao J, Yang G, Wang Y, Yang K, Tumukunde E, Wang S, Yuan J. The membrane mucin Msb2 regulates aflatoxin biosynthesis and pathogenicity in fungus Aspergillus flavus. Microb Biotechnol 2020; 14:628-642. [PMID: 33159717 PMCID: PMC7936294 DOI: 10.1111/1751-7915.13701] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 10/17/2020] [Accepted: 10/20/2020] [Indexed: 12/12/2022] Open
Abstract
As a pathogenic fungus, Aspergillus flavus can produce carcinogenic aflatoxins (AFs), which poses a great threat to crops and animals. Msb2, the signalling mucin protein, is a part of mitogen‐activated protein kinase (MAPK) pathway which contributes to a range of physiological processes. In this study, the roles of membrane mucin Msb2 were explored in A. flavus by the application of gene disruption. The deletion of msb2 gene (Δmsb2) caused defects in vegetative growth, sporulation and sclerotia formation when compared to WT and complement strain (Δmsb2C) in A. flavus. Using thin‐layer chromatography (TLC) and high‐performance liquid chromatography (HPLC) analysis, it was found that deletion of msb2 down‐regulated aflatoxin B1 (AFB1) synthesis and decreased the infection capacity of A. flavus. Consistently, Msb2 responds to cell wall stress and osmotic stress by positively regulating the phosphorylation of MAP kinase. Notably, Δmsb2 mutant exhibited cell wall defect, and it was more sensitive to inhibitor caspofungin when compared to WT and Δmsb2C. Taking together, these results revealed that Msb2 plays key roles in morphological development process, stresses adaptation, secondary metabolism and pathogenicity in fungus A. flavus.
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Affiliation(s)
- Ling Qin
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Ding Li
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Jiaru Zhao
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Guang Yang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Yinchun Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Kunlong Yang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Elisabeth Tumukunde
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Shihua Wang
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
| | - Jun Yuan
- Key Laboratory of Pathogenic Fungi and Mycotoxins of Fujian Province, Key Laboratory of Biopesticide and Chemical Biology of Education Ministry, School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China
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The Regulatory Properties of the Ccr4-Not Complex. Cells 2020; 9:cells9112379. [PMID: 33138308 PMCID: PMC7692201 DOI: 10.3390/cells9112379] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 10/21/2020] [Accepted: 10/26/2020] [Indexed: 12/12/2022] Open
Abstract
The mammalian Ccr4–Not complex, carbon catabolite repression 4 (Ccr4)-negative on TATA-less (Not), is a large, highly conserved, multifunctional assembly of proteins that acts at different cellular levels to regulate gene expression. In the nucleus, it is involved in the regulation of the cell cycle, chromatin modification, activation and inhibition of transcription initiation, control of transcription elongation, RNA export, nuclear RNA surveillance, and DNA damage repair. In the cytoplasm, the Ccr4–Not complex plays a central role in mRNA decay and affects protein quality control. Most of our original knowledge of the Ccr4–Not complex is derived, primarily, from studies in yeast. More recent studies have shown that the mammalian complex has a comparable structure and similar properties. In this review, we summarize the evidence for the multiple roles of both the yeast and mammalian Ccr4–Not complexes, highlighting their similarities.
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Brommel CM, Cooney AL, Sinn PL. Adeno-Associated Virus-Based Gene Therapy for Lifelong Correction of Genetic Disease. Hum Gene Ther 2020; 31:985-995. [PMID: 32718227 PMCID: PMC7495917 DOI: 10.1089/hum.2020.138] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 07/27/2020] [Indexed: 12/27/2022] Open
Abstract
The list of successful gene therapy trials using adeno-associated virus (AAV)-based vectors continues to grow and includes a wide range of monogenic diseases. Replication incompetent AAV genomes typically remain episomal and expression dilutes as cells divide and die. Consequently, long-term transgene expression from AAV is best suited for quiescent cell types, such as retinal cells, myocytes, or neurons. For genetic diseases that involve cells with steady turnover, AAV-conferred correction may require routine readministration, where every dose carries the risk of developing an adaptive immune response that renders treatment ineffective. Here, we discuss innovative approaches to permanently modify the host genome using AAV-based platforms, thus potentially requiring only a single dose. Such approaches include using AAV delivery of DNA transposons, homologous recombination templates into safe harbors, and nucleases for targeting integration. In tissues with continual cell turnover, genetic modification of progenitor cell populations will help ensure persistent therapeutic outcomes. Combining the safety profile of AAV-based gene therapy vectors with the ability to integrate a therapeutic transgene creates novel solutions to the challenge of lifelong curative treatments for human genetic diseases.
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Affiliation(s)
| | - Ashley L. Cooney
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA
| | - Patrick L. Sinn
- Program in Molecular Medicine, University of Iowa, Iowa City, Iowa, USA
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, USA
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31
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Pérez-Calero C, Bayona-Feliu A, Xue X, Barroso SI, Muñoz S, González-Basallote VM, Sung P, Aguilera A. UAP56/DDX39B is a major cotranscriptional RNA-DNA helicase that unwinds harmful R loops genome-wide. Genes Dev 2020; 34:898-912. [PMID: 32439635 PMCID: PMC7328515 DOI: 10.1101/gad.336024.119] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 04/20/2020] [Indexed: 01/10/2023]
Abstract
Nonscheduled R loops represent a major source of DNA damage and replication stress. Cells have different ways to prevent R-loop accumulation. One mechanism relies on the conserved THO complex in association with cotranscriptional RNA processing factors including the RNA-dependent ATPase UAP56/DDX39B and histone modifiers such as the SIN3 deacetylase in humans. We investigated the function of UAP56/DDX39B in R-loop removal. We show that UAP56 depletion causes R-loop accumulation, R-loop-mediated genome instability, and replication fork stalling. We demonstrate an RNA-DNA helicase activity in UAP56 and show that its overexpression suppresses R loops and genome instability induced by depleting five different unrelated factors. UAP56/DDX39B localizes to active chromatin and prevents the accumulation of RNA-DNA hybrids over the entire genome. We propose that, in addition to its RNA processing role, UAP56/DDX39B is a key helicase required to eliminate harmful cotranscriptional RNA structures that otherwise would block transcription and replication.
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Affiliation(s)
- Carmen Pérez-Calero
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER) Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla 41092, Spain
| | - Aleix Bayona-Feliu
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER) Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla 41092, Spain
| | - Xiaoyu Xue
- Molecular Biophysics and Biochemistry, School of Medicine, University of Yale, New Haven, Connecticut 06510, USA
- Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas 78666, USA
| | - Sonia I Barroso
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER) Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla 41092, Spain
| | - Sergio Muñoz
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER) Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla 41092, Spain
| | - Víctor M González-Basallote
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER) Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla 41092, Spain
| | - Patrick Sung
- Molecular Biophysics and Biochemistry, School of Medicine, University of Yale, New Haven, Connecticut 06510, USA
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA
| | - Andrés Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa (CABIMER) Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Sevilla 41092, Spain
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New insight into the biology of R-loops. Mutat Res 2020; 821:111711. [PMID: 32516653 DOI: 10.1016/j.mrfmmm.2020.111711] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 05/22/2020] [Accepted: 05/23/2020] [Indexed: 11/24/2022]
Abstract
R-loops form when RNA hybridizes with its template DNA generating a three-stranded structure leaving a displaced single strand non-template DNA. During transcription negative supercoiling of DNA behind the advancing RNA polymerase will facilitate the formation of R-loops by the nascent RNA as the DNA is under wound to facilitate transcription. In theory R-loops are classified into pathological and non-pathological depending on the context of its formation. R-loop which are formed normally in various physiological events like in gene regulation and at immunoglobulin class switch regions are considered non-pathological, whereas abnormally stable R-loop which leads to genomic instability are considered pathological. Although pathological R-loop formation is a rare event but once formed completely blocks transcription, mRNA export, elevates mutagenesis, and inhibits gene expression. Hence, R-loop either prevents or induces genomic instability indirectly and are potentially an endogenous source of DNA lesion. Although the existence of R-loop has been reported few decades ago, but only recently we have gained knowledge about its formation and resolution in cells due to the availability of reagents. R-loop biology has generated immense interest in past few years since it connects the important biological processes such as transcription, mRNA splicing, DNA replication, recombination and repair. In this review I will focus on the recent progress made about formation and resolution of R-loop, based on the methodologies that are currently available to study R-loop using biochemical, cell biology and molecular biology approaches.
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Paiva ALB, Matavel A, Silva BCS, Guerra-Duarte C, Diniz MRV. Gene sequence analysis of toxins from the spider Phoneutria nigriventer revealed an intronless feature. J Venom Anim Toxins Incl Trop Dis 2020; 26:e20190075. [PMID: 32395122 PMCID: PMC7199488 DOI: 10.1590/1678-9199-jvatitd-2019-0075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 03/18/2020] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Phoneutria nigriventer spider venom contains several cysteine-rich peptide toxins that act on different ion channels. Despite extensive studies on its venom and description of cDNA sequences of several of its toxin precursors, the gene structure of these toxins remains unknown. METHODS Genomic regions encoding the precursors of three previously characterized P. nigriventer toxins - PnTx1, PnTx2-5 and PnTx4(5-5) - were amplified by PCR using specific primers. PCR fragments were cloned and sequenced. Obtained sequences were compared with their corresponding cDNA sequences. RESULTS The size of PCR fragments obtained and sequences corresponding to genomic regions encoding for the toxin precursors matched their cDNA sequences. CONCLUSIONS Despite a few nucleotide substitutions in the genomic regions encoding for the toxin precursors when compared with cDNA sequences, the results of the present work indicate that P. nigriventer toxins do not contain introns in their genes sequences.
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Affiliation(s)
| | - Alessandra Matavel
- Diretoria de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias
(FUNED), Belo Horizonte, MG, Brazil
| | - Bruno César Souza Silva
- Universidade Federal de Minas Gerais (UFMG), Programa Interunidades
de Pós-graduação em Bioinformática (ICB), Belo Horizonte, MG, Brazil
| | - Clara Guerra-Duarte
- Diretoria de Pesquisa e Desenvolvimento, Fundação Ezequiel Dias
(FUNED), Belo Horizonte, MG, Brazil
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34
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Argaud D, Boulanger MC, Chignon A, Mkannez G, Mathieu P. Enhancer-mediated enrichment of interacting JMJD3-DDX21 to ENPP2 locus prevents R-loop formation and promotes transcription. Nucleic Acids Res 2019; 47:8424-8438. [PMID: 31251802 PMCID: PMC6895255 DOI: 10.1093/nar/gkz560] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 06/17/2019] [Accepted: 06/25/2019] [Indexed: 12/11/2022] Open
Abstract
ENPP2, which encodes for the enzyme autotaxin (ATX), is overexpressed during chronic inflammatory diseases and various cancers. However, the molecular mechanism involved in the ENPP2 transcription remains elusive. Here, in HEK 293T cells, we demonstrated that lipopolysaccharide (LPS) increased the transcription process at ENPP2 locus through a NF-кB pathway and a reduction of H3K27me3 level, a histone repressive mark, by the demethylase UTX. Simultaneously, the H3K27me3 demethylase JMJD3/KDM6B was recruited to the transcription start site (TSS), within the gene body and controlled the expression of ENPP2 in a non-enzymatic manner. Mass spectrometry data revealed a novel interaction for JMJD3 with DDX21, a RNA helicase that unwinds R-loops created by nascent transcript and DNA template. Upon LPS treatment, JMJD3 is necessary for DDX21 recruitment at ENPP2 locus allowing the resolution of aberrant R-loops. CRISPR-Cas9-mediated deletion of a distant-acting enhancer decreased the expression of ENPP2 and lowered the recruitment of JMJD3–DDX21 complex at TSS and its progression through the gene body. Taken together, these findings revealed that enhancer-mediated enrichment of novel JMJD3–DDX21 interaction at ENPP2 locus is necessary for nascent transcript synthesis via the resolution of aberrant R-loops formation in response to inflammatory stimulus.
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Affiliation(s)
- Deborah Argaud
- Laboratory of Cardiovascular Pathobiology, Quebec Heart and Lung Institute/Research Center, Department of Surgery, Laval University, Quebec G1V-4G5, Canada
| | - Marie-Chloé Boulanger
- Laboratory of Cardiovascular Pathobiology, Quebec Heart and Lung Institute/Research Center, Department of Surgery, Laval University, Quebec G1V-4G5, Canada
| | - Arnaud Chignon
- Laboratory of Cardiovascular Pathobiology, Quebec Heart and Lung Institute/Research Center, Department of Surgery, Laval University, Quebec G1V-4G5, Canada
| | - Ghada Mkannez
- Laboratory of Cardiovascular Pathobiology, Quebec Heart and Lung Institute/Research Center, Department of Surgery, Laval University, Quebec G1V-4G5, Canada
| | - Patrick Mathieu
- Laboratory of Cardiovascular Pathobiology, Quebec Heart and Lung Institute/Research Center, Department of Surgery, Laval University, Quebec G1V-4G5, Canada
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Pan L, Wang H, Luo J, Zeng J, Pi J, Liu H, Liu C, Ba X, Qu X, Xiang Y, Boldogh I, Qin X. Epigenetic regulation of TIMP1 expression by 8-oxoguanine DNA glycosylase-1 binding to DNA:RNA hybrid. FASEB J 2019; 33:14159-14170. [PMID: 31652414 DOI: 10.1096/fj.201900993rr] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
8-Oxoguanine DNA glycosylase-1 (OGG1)-initiated base excision repair pathway is primarily responsible for 7, 8-dihydro-8-oxoguanine (8-oxoG) removal from DNA. Recent studies, however, have shown that 8-oxoG in gene regulatory elements may serve as an epigenetic mark, and OGG1 has distinct functions in modulating gene expression. Genome-wide mapping of oxidative stress-induced OGG1 enrichment within introns was documented, but its significance has not yet been fully characterized. Here, we explored whether OGG1 recruited to intron 1 of tissue inhibitor of metalloproteinase-1 (TIMP1) gene and modulated its expression. Using chromatin and DNA:RNA hybrid immunoprecipitation assays, we report recruitment of OGG1 to the DNA:RNA hybrid in intron 1, where it increases nascent RNA but lowers mRNA levels in O3-exposed human airway epithelial cells and mouse lungs. Decrease in TIMP1 expression is alleviated by antioxidant administration, small interfering RNA depletion, or inhibition of OGG1 binding to its genomic substrate. In vitro studies revealed direct interaction between OGG1 and 8-oxoG containing DNA:RNA hybrid, without excision of its substrate. Inhibition of OGG1 binding to DNA:RNA hybrid translated into an increase in TIMP1 expression and a decrease in oxidant-induced lung inflammatory responses as well as airway remodeling. Data documented here reveal a novel molecular link between OGG1 at damaged sites and transcription dynamics that may contribute to oxidative stress-induced cellular and tissue responses.-Pan, L., Wang, H., Luo, J., Zeng, J., Pi, J., Liu, H., Liu, C., Ba, X., Qu, X., Xiang, Y., Boldogh, I., Qin, X. Epigenetic regulation of TIMP1 expression by 8-oxoguanine DNA glycosylase-1 binding to DNA:RNA hybrid.
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Affiliation(s)
- Lang Pan
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Hui Wang
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Jinhua Luo
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Ji Zeng
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Jiao Pi
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Huijun Liu
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Chi Liu
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Xueqing Ba
- The Key Laboratory of Molecular Epigenetics, Ministry of Education, Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
| | - Xiangping Qu
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Yang Xiang
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
| | - Istvan Boldogh
- Department of Microbiology and Immunology, School of Medicine, The University of Texas Medical Branch at Galveston, Galveston, Texas, USA
| | - Xiaoqun Qin
- Department of Physiology, School of Basic Medicine, Xiangya Medical School, Central South University, Changsha, China
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Prister LL, Ozer EA, Cahoon LA, Seifert HS. Transcriptional initiation of a small RNA, not R-loop stability, dictates the frequency of pilin antigenic variation in Neisseria gonorrhoeae. Mol Microbiol 2019; 112:1219-1234. [PMID: 31338863 PMCID: PMC6800796 DOI: 10.1111/mmi.14356] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/20/2019] [Indexed: 02/06/2023]
Abstract
Neisseria gonorrhoeae, the sole causative agent of gonorrhea, constitutively undergoes diversification of the Type IV pilus. Gene conversion occurs between one of the several donor silent copies located in distinct loci and the recipient pilE gene, encoding the major pilin subunit of the pilus. A guanine quadruplex (G4) DNA structure and a cis-acting sRNA (G4-sRNA) are located upstream of the pilE gene and both are required for pilin antigenic variation (Av). We show that the reduced sRNA transcription lowers pilin Av frequencies. Extended transcriptional elongation is not required for Av, since limiting the transcript to 32 nt allows for normal Av frequencies. Using chromatin immunoprecipitation (ChIP) assays, we show that cellular G4s are less abundant when sRNA transcription is lower. In addition, using ChIP, we demonstrate that the G4-sRNA forms a stable RNA:DNA hybrid (R-loop) with its template strand. However, modulating R-loop levels by controlling RNase HI expression does not alter G4 abundance quantified through ChIP. Since pilin Av frequencies were not altered when modulating R-loop levels by controlling RNase HI expression, we conclude that transcription of the sRNA is necessary, but stable R-loops are not required to promote pilin Av.
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Affiliation(s)
- Lauren L Prister
- Department of Microbiology-Immunology, DiseaseNorthwestern University Feinberg School of Medicine, Chicago, IL US
| | - Egon A Ozer
- Department of Microbiology-Immunology, DiseaseNorthwestern University Feinberg School of Medicine, Chicago, IL US
- Department of Medicine, Division of Infectious DiseaseNorthwestern University Feinberg School of Medicine, Chicago, IL US
| | - Laty A Cahoon
- Department of Microbiology-Immunology, DiseaseNorthwestern University Feinberg School of Medicine, Chicago, IL US
| | - H Steven Seifert
- Department of Microbiology-Immunology, DiseaseNorthwestern University Feinberg School of Medicine, Chicago, IL US
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Briggs E, Crouch K, Lemgruber L, Hamilton G, Lapsley C, McCulloch R. Trypanosoma brucei ribonuclease H2A is an essential R-loop processing enzyme whose loss causes DNA damage during transcription initiation and antigenic variation. Nucleic Acids Res 2019; 47:9180-9197. [PMID: 31350892 PMCID: PMC6753483 DOI: 10.1093/nar/gkz644] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 07/09/2019] [Accepted: 07/16/2019] [Indexed: 12/21/2022] Open
Abstract
Ribonucleotides represent a threat to DNA genome stability and transmission. Two types of Ribonuclease H (RNase H) excise ribonucleotides when they form part of the DNA strand, or hydrolyse RNA when it base-pairs with DNA in structures termed R-loops. Loss of either RNase H is lethal in mammals, whereas yeast survives the absence of both enzymes. RNase H1 loss is tolerated by the parasite Trypanosoma brucei but no work has examined the function of RNase H2. Here we show that loss of T. brucei RNase H2 (TbRH2A) leads to growth and cell cycle arrest that is concomitant with accumulation of nuclear damage at sites of RNA polymerase (Pol) II transcription initiation, revealing a novel and critical role for RNase H2. Differential gene expression analysis reveals limited overall changes in RNA levels for RNA Pol II genes after TbRH2A loss, but increased perturbation of nucleotide metabolic genes. Finally, we show that TbRH2A loss causes R-loop and DNA damage accumulation in telomeric RNA Pol I transcription sites, also leading to altered gene expression. Thus, we demonstrate separation of function between two nuclear T. brucei RNase H enzymes during RNA Pol II transcription, but overlap in function during RNA Pol I-mediated gene expression during host immune evasion.
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Affiliation(s)
- Emma Briggs
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow G12 8TA, UK
| | - Kathryn Crouch
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow G12 8TA, UK
| | - Leandro Lemgruber
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow G12 8TA, UK
| | - Graham Hamilton
- Glasgow Polyomics, University of Glasgow, Wolfson Wohl Cancer Research Centre, Garscube Estate, Switchback Rd, Bearsden G61 1QH, UK
| | - Craig Lapsley
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow G12 8TA, UK
| | - Richard McCulloch
- The Wellcome Centre for Integrative Parasitology, University of Glasgow, College of Medical, Veterinary and Life Sciences, Institute of Infection, Immunity and Inflammation, Sir Graeme Davies Building, 120 University Place, Glasgow G12 8TA, UK
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Xia Y, Zheng KW, He YD, Liu HH, Wen CJ, Hao YH, Tan Z. Transmission of dynamic supercoiling in linear and multi-way branched DNAs and its regulation revealed by a fluorescent G-quadruplex torsion sensor. Nucleic Acids Res 2019; 46:7418-7424. [PMID: 29982790 PMCID: PMC6101514 DOI: 10.1093/nar/gky534] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 05/31/2018] [Indexed: 01/20/2023] Open
Abstract
DNA supercoiling is an important regulator of gene activity. The transmission of transcription-generated supercoiling wave along a DNA helix provides a way for a gene being transcribed to communicate with and regulate its neighboring genes. Currently, the dynamic behavior of supercoiling transmission remains unclear owing to the lack of a suitable tool for detecting the dynamics of supercoiling transmission. In this work, we established a torsion sensor that quantitatively monitors supercoiling transmission in real time in DNA. Using this sensor, we studied the transmission of transcriptionally generated negative supercoiling in linear and multi-way DNA duplexes. We found that transcription-generated dynamic supercoiling not only transmits along linear DNA duplex but also equally diverges at and proceeds through multi-way DNA junctions. We also show that such a process is regulated by DNA–protein interactions and non-canonical DNA structures in the path of supercoiling transmission. These results imply a transcription-coupled mechanism of dynamic supercoiling-mediated intra- and inter-chromosomal signal transduction pathway and their regulation in DNA.
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Affiliation(s)
- Ye Xia
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China.,University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Ke-Wei Zheng
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Yi-de He
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Hong-He Liu
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Cui-Jiao Wen
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Yu-Hua Hao
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
| | - Zheng Tan
- State Key Laboratory of Membrane Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
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Jalan M, Olsen KS, Powell SN. Emerging Roles of RAD52 in Genome Maintenance. Cancers (Basel) 2019; 11:E1038. [PMID: 31340507 PMCID: PMC6679097 DOI: 10.3390/cancers11071038] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 07/17/2019] [Accepted: 07/18/2019] [Indexed: 12/22/2022] Open
Abstract
The maintenance of genome integrity is critical for cell survival. Homologous recombination (HR) is considered the major error-free repair pathway in combatting endogenously generated double-stranded lesions in DNA. Nevertheless, a number of alternative repair pathways have been described as protectors of genome stability, especially in HR-deficient cells. One of the factors that appears to have a role in many of these pathways is human RAD52, a DNA repair protein that was previously considered to be dispensable due to a lack of an observable phenotype in knock-out mice. In later studies, RAD52 deficiency has been shown to be synthetically lethal with defects in BRCA genes, making RAD52 an attractive therapeutic target, particularly in the context of BRCA-deficient tumors.
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Affiliation(s)
- Manisha Jalan
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Kyrie S Olsen
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Simon N Powell
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA.
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Abstract
Genome replication involves dealing with obstacles that can result from DNA damage but also from chromatin alterations, topological stress, tightly bound proteins or non-B DNA structures such as R loops. Experimental evidence reveals that an engaged transcription machinery at the DNA can either enhance such obstacles or be an obstacle itself. Thus, transcription can become a potentially hazardous process promoting localized replication fork hindrance and stress, which would ultimately cause genome instability, a hallmark of cancer cells. Understanding the causes behind transcription-replication conflicts as well as how the cell resolves them to sustain genome integrity is the aim of this review.
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41
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Chen F, Fengling Lai, Luo M, Han YS, Cheng H, Zhou R. The genome-wide landscape of small insertion and deletion mutations in Monopterus albus. J Genet Genomics 2019; 46:75-86. [PMID: 30867123 DOI: 10.1016/j.jgg.2019.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 12/21/2018] [Accepted: 02/01/2019] [Indexed: 11/17/2022]
Abstract
Insertion and deletion (indel) mutations, which can trigger single nucleotide substitutions on the flanking regions of genes, may generate abundant materials for disease defense, reproduction, species survival and evolution. However, genetic and evolutionary mechanisms of indels remain elusive. We establish a comparative genome-transcriptome-alignment approach for a large-scale identification of indels in Monopterus population. Over 2000 indels in 1738 indel genes, including 1-21 bp deletions and 1-15 bp insertions, were detected. Each indel gene had ∼1.1 deletions/insertions, and 2-4 alleles in population. Frequencies of deletions were prominently higher than those of insertions on both genome and population levels. Most of the indels led to in frame mutations with multiples of three and majorly occurred in non-domain regions, indicating functional constraint or tolerance of the indels. All indel genes showed higher expression levels than non-indel genes during sex reversal. Slide window analysis of global expression levels in gonads showed a significant positive correlation with indel density in the genome. Moreover, indel genes were evolutionarily conserved and evolved slowly compared to non-indel genes. Notably, population genetic structure of indels revealed divergent evolution of Monopterus population, as bottleneck effect of biogeographic isolation by Taiwan Strait, China.
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Affiliation(s)
- Feng Chen
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Fengling Lai
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Majing Luo
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China
| | - Yu-San Han
- Institute of Fisheries Science, College of Life Science, "National Taiwan University", Taipei, 10617, Taiwan, China
| | - Hanhua Cheng
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
| | - Rongjia Zhou
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
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42
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Datta A, Brosh RM. Holding All the Cards-How Fanconi Anemia Proteins Deal with Replication Stress and Preserve Genomic Stability. Genes (Basel) 2019; 10:genes10020170. [PMID: 30813363 PMCID: PMC6409899 DOI: 10.3390/genes10020170] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Revised: 02/14/2019] [Accepted: 02/15/2019] [Indexed: 12/18/2022] Open
Abstract
Fanconi anemia (FA) is a hereditary chromosomal instability disorder often displaying congenital abnormalities and characterized by a predisposition to progressive bone marrow failure (BMF) and cancer. Over the last 25 years since the discovery of the first linkage of genetic mutations to FA, its molecular genetic landscape has expanded tremendously as it became apparent that FA is a disease characterized by a defect in a specific DNA repair pathway responsible for the correction of covalent cross-links between the two complementary strands of the DNA double helix. This pathway has become increasingly complex, with the discovery of now over 20 FA-linked genes implicated in interstrand cross-link (ICL) repair. Moreover, gene products known to be involved in double-strand break (DSB) repair, mismatch repair (MMR), and nucleotide excision repair (NER) play roles in the ICL response and repair of associated DNA damage. While ICL repair is predominantly coupled with DNA replication, it also can occur in non-replicating cells. DNA damage accumulation and hematopoietic stem cell failure are thought to contribute to the increased inflammation and oxidative stress prevalent in FA. Adding to its confounding nature, certain FA gene products are also engaged in the response to replication stress, caused endogenously or by agents other than ICL-inducing drugs. In this review, we discuss the mechanistic aspects of the FA pathway and the molecular defects leading to elevated replication stress believed to underlie the cellular phenotypes and clinical features of FA.
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Affiliation(s)
- Arindam Datta
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, MD 21224, USA.
| | - Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, NIH, NIH Biomedical Research Center, Baltimore, MD 21224, USA.
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Affiliation(s)
- Lauren L. Prister
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
| | - H. Steven Seifert
- Department of Microbiology-Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States of America
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Chakraborty P, Huang JTJ, Hiom K. DHX9 helicase promotes R-loop formation in cells with impaired RNA splicing. Nat Commun 2018; 9:4346. [PMID: 30341290 PMCID: PMC6195550 DOI: 10.1038/s41467-018-06677-1] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Accepted: 09/06/2018] [Indexed: 01/05/2023] Open
Abstract
R-loops are stable nucleic acid structures that have important physiological functions, but which also pose a significant threat to genomic stability. Increased R-loops cause replication stress and chromosome fragility and have been associated with diseases such as neurodegeneration and cancer. Although excessive R-loops are a feature of cells that are defective in RNA processing, what causes them to form is unclear. Here, we demonstrate that DHX9 (RNA helicase A) promotes the formation of pathological and non-pathological R-loops. In the absence of splicing factors, formation of R-loops correlates with the prolonged association of DHX9 with RNA Polymerase II (RNA Pol II). This leads to the production of DNA–RNA hybrid, which traps RNA Pol II on chromatin with the potential to block DNA replication. Our data provide a molecular mechanism for the formation of R-loops that is relevant to neurodegenerative diseases and cancers in which deregulated RNA processing is a feature. Unresolved R-loops can represent a threat to genome stability. Here the authors reveal that DHX9 helicase can promote R-loop formation in the absence of splicing factors SFPQ and SF3B3.
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Affiliation(s)
- Prasun Chakraborty
- Division of Cellular Medicine, School of Medicine, University of Dundee, Scotland, UK
| | - Jeffrey T J Huang
- Biomarker and Drug Analysis Core Facility, School of Medicine, University of Dundee, Scotland, UK
| | - Kevin Hiom
- Division of Cellular Medicine, School of Medicine, University of Dundee, Scotland, UK.
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Sivaramakrishnan P, Gordon AJE, Halliday JA, Herman C. How Acts of Infidelity Promote DNA Break Repair: Collision and Collusion Between DNA Repair and Transcription. Bioessays 2018; 40:e1800045. [PMID: 30091472 PMCID: PMC6334755 DOI: 10.1002/bies.201800045] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 07/07/2018] [Indexed: 12/20/2022]
Abstract
Transcription is a fundamental cellular process and the first step in gene regulation. Although RNA polymerase (RNAP) is highly processive, in growing cells the progression of transcription can be hindered by obstacles on the DNA template, such as damaged DNA. The authors recent findings highlight a trade-off between transcription fidelity and DNA break repair. While a lot of work has focused on the interaction between transcription and nucleotide excision repair, less is known about how transcription influences the repair of DNA breaks. The authors suggest that when the cell experiences stress from DNA breaks, the control of RNAP processivity affects the balance between preserving transcription integrity and DNA repair. Here, how the conflict between transcription and DNA double-strand break (DSB) repair threatens the integrity of both RNA and DNA are discussed. In reviewing this field, the authors speculate on cellular paradigms where this equilibrium is well sustained, and instances where the maintenance of transcription fidelity is favored over genome stability.
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Affiliation(s)
- Priya Sivaramakrishnan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Alasdair J E Gordon
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jennifer A Halliday
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Christophe Herman
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Baylor College of Medicine, Dan L. Duncan Comprehensive Cancer Center, Houston, TX 77030, USA
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030, USA
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46
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Owiti N, Wei S, Bhagwat AS, Kim N. Unscheduled DNA synthesis leads to elevated uracil residues at highly transcribed genomic loci in Saccharomyces cerevisiae. PLoS Genet 2018; 14:e1007516. [PMID: 30016327 PMCID: PMC6063437 DOI: 10.1371/journal.pgen.1007516] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 07/27/2018] [Accepted: 06/26/2018] [Indexed: 12/31/2022] Open
Abstract
Recombination and mutagenesis are elevated by active transcription. The correlation between transcription and genome instability is largely explained by the topological and structural changes in DNA and the associated physical obstacles generated by the transcription machinery. However, such explanation does not directly account for the unique types of mutations originating from the non-canonical residues, uracil or ribonucleotide, which are also elevated at highly transcribed regions. Based on the previous findings that abasic (AP) lesions derived from the uracil residues incorporated into DNA in place of thymine constitute a major component of the transcription-associated mutations in yeast, we formed the hypothesis that DNA synthesis ensuing from the repair of the transcription-induced DNA damage provide the opportunity for uracil-incorporation. In support of this hypothesis, we show here the positive correlation between the level of transcription and the density of uracil residues in the yeast genome indirectly through the mutations generated by the glycosylase that excise undamaged cytosine as well as uracil. The higher uracil-density at actively transcribed regions is confirmed by the long-amplicon PCR analysis. We also show that the uracil-associated mutations at a highly transcribed region are elevated by the induced DNA damage and reduced by the overexpression of a dUTP-catalyzing enzyme Dut1 in G1- or G2-phases of the cell cycle. Overall, our results show that the DNA composition can be modified to include higher uracil-content through the non-replicative, repair-associated DNA synthesis. Uracil in DNA, a major source of spontaneous mutations, can occur through the deamination of cytosine residues or through the direct incorporation of dUTP by DNA polymerases. Recent studies in yeast have shown that the uracil-associated mutations occur more frequently at highly transcribed regions. Because the reduction in dUTP pool decreased these mutations, it was postulated that the extent of uracil-incorporation into DNA is significantly affected by the local transcription activity. We show here that the higher transcription rate does correlate with the higher uracil-density in the yeast genome. We further provide multiple lines of evidence supporting a model of uracil-incorporation into DNA that is dependent on the repair synthesis of transcription-associated DNA damage.
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Affiliation(s)
- Norah Owiti
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center at Houston, Houston, TX United States of America
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX United States of America
| | - Shanqiao Wei
- Department of Chemistry, Wayne State University, Detroit, MI United States of America
| | - Ashok S. Bhagwat
- Department of Chemistry, Wayne State University, Detroit, MI United States of America
- Department of Biochemistry, Immunology and Microbiology, Wayne State University, Detroit, MI United States of America
| | - Nayun Kim
- Department of Microbiology and Molecular Genetics, University of Texas Health Science Center at Houston, Houston, TX United States of America
- The University of Texas Graduate School of Biomedical Sciences, Houston, TX United States of America
- * E-mail:
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47
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Multiple signaling kinases target Mrc1 to prevent genomic instability triggered by transcription-replication conflicts. Nat Commun 2018; 9:379. [PMID: 29371596 PMCID: PMC5785523 DOI: 10.1038/s41467-017-02756-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 12/21/2017] [Indexed: 02/05/2023] Open
Abstract
Conflicts between replication and transcription machineries represent a major source of genomic instability and cells have evolved strategies to prevent such conflicts. However, little is known regarding how cells cope with sudden increases of transcription while replicating. Here, we report the existence of a general mechanism for the protection of genomic integrity upon transcriptional outbursts in S phase that is mediated by Mrc1. The N-terminal phosphorylation of Mrc1 blocked replication and prevented transcription-associated recombination (TAR) and genomic instability during stress-induced gene expression in S phase. An unbiased kinome screening identified several kinases that phosphorylate Mrc1 at the N terminus upon different environmental stresses. Mrc1 function was not restricted to environmental cues but was also required when unscheduled transcription was triggered by low fitness states such as genomic instability or slow growth. Our data indicate that Mrc1 integrates multiple signals, thereby defining a general safeguard mechanism to protect genomic integrity upon transcriptional outbursts. During S phase of the cell cycle, transcription and replication need to be coordinated in order to avoid conflicts leading to potential genomic instability. Here, the authors find that Mrc1 integrates signals from different kinases to regulate replication during unscheduled transcription events.
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48
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Lin CY, Shukla A, Grady JP, Fink JL, Dray E, Duijf PHG. Translocation Breakpoints Preferentially Occur in Euchromatin and Acrocentric Chromosomes. Cancers (Basel) 2018; 10:cancers10010013. [PMID: 29316705 PMCID: PMC5789363 DOI: 10.3390/cancers10010013] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Revised: 12/11/2017] [Accepted: 01/05/2018] [Indexed: 12/12/2022] Open
Abstract
Chromosomal translocations drive the development of many hematological and some solid cancers. Several factors have been identified to explain the non-random occurrence of translocation breakpoints in the genome. These include chromatin density, gene density and CCCTC-binding factor (CTCF)/cohesin binding site density. However, such factors are at least partially interdependent. Using 13,844 and 1563 karyotypes from human blood and solid cancers, respectively, our multiple regression analysis only identified chromatin density as the primary statistically significant predictor. Specifically, translocation breakpoints preferentially occur in open chromatin. Also, blood and solid tumors show markedly distinct translocation signatures. Strikingly, translocation breakpoints occur significantly more frequently in acrocentric chromosomes than in non-acrocentric chromosomes. Thus, translocations are probably often generated around nucleoli in the inner nucleoplasm, away from the nuclear envelope. Importantly, our findings remain true both in multivariate analyses and after removal of highly recurrent translocations. Finally, we applied pairwise probabilistic co-occurrence modeling. In addition to well-known highly prevalent translocations, such as those resulting in BCR-ABL1 (BCR-ABL) and RUNX1-RUNX1T1 (AML1-ETO) fusion genes, we identified significantly underrepresented translocations with putative fusion genes, which are probably subject to strong negative selection during tumor evolution. Taken together, our findings provide novel insights into the generation and selection of translocations during cancer development.
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Affiliation(s)
- Cheng-Yu Lin
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - Ankit Shukla
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - John P Grady
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - J Lynn Fink
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - Eloise Dray
- Institute of Health and Biomedical Innovation, Queensland University of Technology, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
- Mater Research Institute-The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
| | - Pascal H G Duijf
- University of Queensland Diamantina Institute, The University of Queensland, Translational Research Institute, 37 Kent Street, Brisbane, QLD 4102, Australia.
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49
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Abstract
Ribonucleic acid (RNA) homeostasis is dynamically modulated in response to changing physiological conditions. Tight regulation of RNA abundance through both transcription and degradation determines the amount, timing, and location of protein translation. This balance is of particular importance in neurons, which are among the most metabolically active and morphologically complex cells in the body. As a result, any disruptions in RNA degradation can have dramatic consequences for neuronal health. In this chapter, we will first discuss mechanisms of RNA stabilization and decay. We will then explore how the disruption of these pathways can lead to neurodegenerative disease.
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50
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Sakasai R, Isono M, Wakasugi M, Hashimoto M, Sunatani Y, Matsui T, Shibata A, Matsunaga T, Iwabuchi K. Aquarius is required for proper CtIP expression and homologous recombination repair. Sci Rep 2017; 7:13808. [PMID: 29061988 PMCID: PMC5653829 DOI: 10.1038/s41598-017-13695-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 09/26/2017] [Indexed: 01/01/2023] Open
Abstract
Accumulating evidence indicates that transcription is closely related to DNA damage formation and that the loss of RNA biogenesis factors causes genome instability. However, whether such factors are involved in DNA damage responses remains unclear. We focus here on the RNA helicase Aquarius (AQR), a known R-loop processing factor, and show that its depletion in human cells results in the accumulation of DNA damage during S phase, mediated by R-loop formation. We investigated the involvement of Aquarius in DNA damage responses and found that AQR knockdown decreased DNA damage-induced foci formation of Rad51 and replication protein A, suggesting that Aquarius contributes to homologous recombination (HR)-mediated repair of DNA double-strand breaks (DSBs). Interestingly, the protein level of CtIP, a DSB processing factor, was decreased in AQR-knockdown cells. Exogenous expression of Aquarius partially restored CtIP protein level; however, CtIP overproduction did not rescue defective HR in AQR-knockdown cells. In accordance with these data, Aquarius depletion sensitized cells to genotoxic agents. We propose that Aquarius contributes to the maintenance of genomic stability via regulation of HR by CtIP-dependent and -independent pathways.
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Affiliation(s)
- Ryo Sakasai
- Department of Biochemistry I, Kanazawa Medical University, Ishikawa, Japan
| | - Mayu Isono
- Education and Research Support Center, Gunma University, Ishikawa, Japan
| | - Mitsuo Wakasugi
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Ishikawa, Japan
| | | | - Yumi Sunatani
- Department of Biochemistry I, Kanazawa Medical University, Ishikawa, Japan
| | - Tadashi Matsui
- Department of Biochemistry I, Kanazawa Medical University, Ishikawa, Japan
| | - Atsushi Shibata
- Education and Research Support Center, Gunma University, Ishikawa, Japan
| | - Tsukasa Matsunaga
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Ishikawa, Japan
| | - Kuniyoshi Iwabuchi
- Department of Biochemistry I, Kanazawa Medical University, Ishikawa, Japan.
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